Apparatus and method for fluid handling and sample

ABSTRACT

An apparatus and a method for handling and sampling fluids which comprises principally a nonpumping valve designed so that in operation it moves less than a microliter of fluid, and a pumping valve designed to aspirate a precisely determined amount of fluid into the body of the valve with no more motion than is inherent in the operation of the valve itself and with no change in the physical dimensions of the valve. These valves, when used in combination with a transfer probe and a pump designed to handle minute quantities of fluid, form a precision fluid handling and sampling system which will not contaminate or dilute the fluid to be sampled.

United States Patent [191 Ambrose et al.

[ Aug. 14, 1973 1 APPARATUS AND METHOD FOR FLUID HANDLING AND SAMPLE[73] Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

[22] Filed: Mar. 4, 9171 [21] Appl. No.: 121,146

Related US. Application Data [62] Division of Ser No. 753.199. Aug. 16.i9. l at. No.

[56] References Cited UNITED STATES PATENTS 3,192,968 7/1965 Baruch etal. 141/90 Primary Examiner-Houston S. Bell, Jr. AttorneyWilkin E.Thomas, Jr.

[5 7 ABSTRACT An apparatus and a method for handling and sampling fluidswhich comprises principally a nonpumping valve designed so that inoperation it moves less than a microliter of fluid, and a pumping valvedesigned to aspirate a precisely determined amount of fluid into thebody of the valve with no more motion than is inherent in the operationof the valve itself and with no change in the physical dimensions of thevalve. These valves, when used in combination with a transfer probe anda pump designed to handle minute quantities of fluid, form a precisionfluid handling and sampling system which will not contaminate or dilutethe fluid to be sampled.

3 Claims, 6 Drawing Figures Patented Aug. 14, 1973 3,752,197

2 Sheets-Sheet 1 FIG. A

I? I I 22 I 6 l2 H l8 25 k Patented Aug. 14, 1973 3,752,197

2 Sheets-Sheet 2 FIG.4

APPARATUS AND METHOD FOR FLUID HANDLING AND SAMPLE CROSS REFERENCE TORELATED APPLICATIONS This application is a division of Ser. No. 753,199filed Aug. 16, 1968 by the same inventors. This invention isparticularly related to the subject matter of US. Pat. No. 3,476,515filed 4/26/66, entitled Analytic Test Pack and Process for Analysis byD. R. Johnson et al. (assigned to the assignee of the presentapplication), since the instant invention may be used to transfer thefluid to be tested from its source to the analytic pack described inthat application. It is also related to the subject matter ofapplication Ser. No. 753,197 filed on the same day as this application,entitled Analytic Clinical Analyzer (assigned to the assignee of thepresent application), since the instant invention may be used in thesystem described and claimed therein to introduce the fluid to be testedinto the test packs which are then processed by that system. These crossreferences are merely intended to illustrate and not to restrict thescope and/or use of any of these inventions.

BACKGROUND The field of this invention is a fluid handling and samplingsystem, or more particularly the invention is concerned with the designof a fluid handling and sampling system for use in an analyticinstrument. While fluid handling and sampling systems are not restrictedto use in analytic research, the demands on such systems are frequentlygreatest in such research. Technological advances have increased theprecision of analytic instruments to the point where chemical analysiscan now be performed on minute samples. As a consequence, any fluidhandling and sampling system used in such analysis must be designed withcare to insure precision in the transfer of the fluids involved and toinsure that the sample does not become contaminated or diluted. When theanalysis is being performed by hand, the possibility of human error isalways present. Recently, however, many analytic tests have beenstandardized to the point where they can be performed on automaticanalytic instruments. Human error is no longer present, but the demandson the instrument to reach the level of manual precision, are exacting.

A typical fluid handling and sampling system for use in analyticresearch would include a pump which will handle precise quantities offluid, a valve connected to a transfer probe which is designed to dipinto the fluid to be sampled; and a series of secondary valves connectedto a series of secondary fluid sources. Such a system would permit theintake of a certain amount of a secondary fluid, such as a buffersolution, the uptake of a certain amount of sample fluid, and thedischarge of the sample and secondary fluids into a suitable container.If large amounts of fluid are involved, the requirements for thecomponents of such a system are not particularly stringent. If, however,the amounts of fluid involved are in the microliter range, then therequirements become stringent. In addition, if the sampling system isdesigned to function in an automatic instrument which operatescontinuously there are additional requirements on the durability of thecomponents.

The pump for such a system must be capable of handling small quantitiesof fluid precisely. It is not difficult to design a pump which will dothis for a short period of time, but after a few hundred thousandcycles, wear usually causes leakage. This leakage is on the order ofmicroliters. Hence, to insure precision in the microliter range thepumps must be replaced or repaired. This is time-consuming andexpensive. This invention includes a novel solution to this problemwherein the pump is designed to compensate externally for variations inits dimensions due to constant wear.

The intake valves for such a system, which are designed to introduce thesecondary fluids, are also a source of error. Normally, a valve withmoving parts will move fluid as well as control the flow of fluid. Themovement of the fluid can be referred to as pumping the fluid. Whenlarge quantities of fluid are involved, the small amount of fluid pumpedby the valve in its operation will not introduce appreciable error inthe amount of fluid passing through the valve. When microliters of fluidare involved, the pumping action of the valve will introduce anappreciable error. If the amount of fluid transferred is constant, thiserror would be of a type for which compensation can be made. In manyapplications, however, the amount of fluid transferred is variable andthe constant error introduced by the pumping action of the valve issuperimposed on a variable volume. This type of error is difficult, ifnot impossible, to compensate for; and an effort must be made to designa nonpumping valve for use in such situations. A ball valve with itsfluid shearing motion is one possible design for such a valve, but formany applications where leakage must be kept to a minimum a positiveseating valve is preferable. It is impossible to make a positive seatingvalve which does not move fluid, but it is possible to make such a valvewhich moves less than a certain amount of fluid. Since we are dealingwith microliters of fluid, a nonpumping valve will be, by definition,one that pumps less than a microliter of fluid. The present inventionincludes a valve which is designed to be a nonpumping valve.

The pump and the intake valves for secondary fluid comprise the mainsources of error in the precision of the sampling system. The otherproblem is to keep the sampling system from contaminating the samplefluid. This is a particular problem when the sampling system is designedwith a transfer probe which dips into the sample fluid. In the operationof such a system there is' often a drop of fluid left on the lip of thetransfer probe after the discharge of fluids previously handled. Hence,when the transfer probe is dipped into the sample fluid, the drop on thelip of the transfer probe will contaminate the sample system. Part ofthis problem can be overcome if the transfer probe is cleaned betweeneach use. However, whether the system has been cleaned or not, a drop offluid still remains to dilute the sample. This problem is particularlyacute if the transfer probe is dipped into the sample fluid a number oftimes, or if the sample volume is small. To overcome this problem, thesampling system must be designed so that no fluid remains on the lip ofthe transfer probe. This invention relates to a valve or valve assemblydesigned to aspirate a set amount of fluid from the lip of the transferprobe into the transfer probe so that no contamination or dilutionresults.

Such systems have been the subject of patents in the past. Specifically.U. S. Pat. No. 2,150,760 issued on Mar. 14, 1939 to F. Cozzoli describesan apparatus in which the size of the valve cavity is changed bymanipulation of a diaphram, which forms a wall of the valve cavity, byan external means coupled to the pump. U. S. Pat. No. 2,185,20l issuedon June 2, 1940 to C. Krause, et al. discusses a system in which avacuum is applied from an external pump at various cycles in theoperation of the valve. U. S. Pat. No. 2,619,116 issued on Nov. 25, 1952to J. D. Ralston discusses a resilient seat which upon springing backfrom its original position creates suction. And finally U. S. Pat. No.2,721,008 issued on Oct. 18, 1955 to T. B. Morgan, Jr. discusses asystem in which the valve chamber is composed of two cylinders whichwhen moving relative to one another can change the dimensions of thevalve chamber to create the desired suction. All of these systems willaccomplish the desired result of removing excess liquid from the lip ofthe transfer probe, but at best they are cumbersome devices requiringexternal aids or variations in the physical dimensions of the valvecylinder which limit their usefulness. The present invention includes anovel valve which is designed to accomplish the above result simply andefficiently with no more motion than is inherent in the operation of thevalve itself and with no change in the physical dimensions of the valve.

SUMMARY OF THE INVENTION The present invention comprises a nonpumpingvalve assembly; a pumping valve assembly adapted to aspirate a preciseand predetermined amount of liquid from the lip of its intake-outputopening into the body of the valve; and a precision pump adapted tohandle small quantities of liquid continuously over a long period oftime without the introduction of error caused by leakage in the pump dueto continuous wear. These three elements can be combined to form anintegrated fluid handling and sampling system for use in analyticresearch.

Specifically, the nonpumping valve assembly comprises: an valve enclosedchamber with at least two orifices; at least one movable support means,and a closing means. The support means and the closing means aredisposed within the valve chamber and the support means is adapted tomove the closing means to close off at least one of the openings in thevalve chamber without obstructing the remaining openings. The supportmeans is further adapted so that the free volume in the valve chamberremains substantially constant when the closing means is moved, so thatno fluid is pumped by the motion of the closing means and its associatedsupport means.

The pumping or aspirating valve is composed of the same elements as thenonpumping valve, the difference being that the support means is adaptedso that the free volume in the valve chamber changes when the closingmeans is moved. This causes suction at the intakeoutput opening of thevalve, so the valve can be said to pump. The change in free volume canbe carefully controlled in the design of the valve so that the valve canbe made to pump the precise amount of fluid desired.

The pump is a piston pump comprising: a cylindrical chamber; a pistondisposed within the chamber; and a means for moving the piston. Thepiston itself is comprised of a support means and a deformable capsupported on the support means in such manner that the deformable capcan be deformed externally to conform to the walls of the cylindricalchamber. In this way, even though constant wear occurs, the effect ofthis wear can be overcome by externally deforming the cap.

In the sampling system, the aspirating valve, referred to as theintake-output valve, is generally but not necessarily connected to atransfer probe on the intakeoutput side and to a pump on the oppositeside. Optionally, it can be connected to a series of nonpumping valves,referred to as intake valves, which are connected directly to aplurality of secondary fluid sources, containing fluids such as a washfluid and/or a buffer solution. These intake valves, connected inseriatim, are in turn connected directly to the pump. For convenience inthe discussion that follows, we will assume that there are only twointake valves; one connected to a buffer solution, so that a buffersolution can be added to the sample to be tested, and the otherconnected to a wash fluid, so that the whole system can be cleansed byflushing. This system is meant to be illustrative only. In the casewhere no buffer solution is required and contamination is not a problem,the system can be composed of a single intake-output valve and the pumpwith no intake valves. In the case where a number of tests are to beperformed and a number of different buffer solutions are required, thesystem can be composed of an intake-output valve, as many intake valvesas required, and the pump.

The operation and advantages of the system can best be described withreference to the figures.

FIGS. 1A and 1B illustrate one possible embodiment of a nonpumping valvewhich can be used as the intake valve of a fluid handling and samplingsystem.

FIG. 2 illustrates one possible embodiment of a valve which will pump aprecisely predetermined volume of fluid and can be used as theintake-output valve of a fluid handling and sampling system.

FIG. 3 illustrates a second possible embodiment of a pumping valve.

FIG. 4 illustrates a possible embodiment of a pump for use in a fluidhandling and sampling system.

FIG. 5 is a schematic diagram of one possible embodiment of the fluidhandling and sampling system.

DISCUSSION OF THE DRAWINGS The pump illustrated in FIGS. 1A and 1B is anonpumping valve which will pump less than one microliter of fluid, andcan be used as the intake valve of the fluid handling and samplingsystem. FIG. 1A is a side view of the nonpumping valve. The body ofvalve 11, forming the cylindrical valve chamber 12, is in the shape of acylinder which has been flattened on its side in two places so that theflat sides are parallel to one another. The closing means is in the formof a cylindrical plug or piston 13 which is disposed concentricallywithin the valve chamber and supported therein by support rods 14 and 15which in turn are disposed along the extended axis of the valvecylinder. Support rod 14 passes through the end of the valve chamber 16,through the body of the valve 11, and through the end plug 17 to theexterior of the valve. Support rod 15 passes through end plug 18 to theexterior of the valve. The valve chamber 12 has an opening 19 in end 16through which support rod 14 passes. This opening is expanded into achannel 20 which extends into the valve cylinder and is concentric withsupport rod 14. Channel 20 is connected by two other channels, 21 and22., to the flattened sides of the valve cylinder. The expanded portionof these channels adjacent to the flat surface of the valve cylinder areadapted to hold a gasket which will seal one of these, channel 21, to asimilar channel in either another intake valve or the pump, as will bediscussed later, and the other channel 22 to a similar channel in theintake-output valve, as will be discussed later. The valve chamber 12also has an opening 23 in its side with a channel leading to the outsideof the valve. This can be seen with reference to FIG. 1B which is a topview of this embodiment of the nonpumping valve. The opening 23 isconnected through channel 24 to the outside of the valve and normally toa source of secondary fluid, not shown, through tube 25. In whatfollows, this opening 23 and the channel 24 will be referred tocollectively as the intake opening. Returning to FIG. 1A, thecylindrical plug 13 has a diameter less than that of the valve chamber12 so that it can be moved freely within the valve chamber withoutblocking the intake opening 23. The diameter of the cylindrical plug 13is greater than the diameter of the opening 19 so that when the plug isseated at the end of the valve chamber 16 in which the opening islocated, the opening will be blocked, effectively closing the valve. Theposition of the plug 13 in the valve chamber can be manipulatedexternally either manually or by any suitable device which can be madeto operate on the end of either support rod 14 or support rod 15. Thesystem can optionally be spring loaded as shown in FIG. 1A, where spring25 will cause the cylindrical plug 13 to return to the closed positionwhen the force is removed from whichever support rod is being used tomanipulate the valve. Optionally the spring can be positioned so thatthe closing means will return to the open position. Mechanisms forspring loading are well known to those skilled in the art so themechanism is only indicated by the inclusion of a spring in FIG. 1A.Finally all the seals in the valve which can leak are sealed withO-rings or Quad-rings as indicated by the cross hatched area in FIG. 1A;and the positions of the plug and valve body through which the supportrods pass are suitably undercut to allow free motion of the support rod.All of these procedures are well known to those skilled in the art ofvalve construction.

The novel feature of this valve is the fact that in operation it willnot pump fluid. The two support rods 14 and 15 are of substantiallyidentical diameters so that, in the motion of the closing means 13, asone rod moves out of the chamber 12 it is replaced with an equal volumeof the other rod. In this way the free volume in the chamber remainsconstant and no fluid is pumped. Nonpumping has been defined, herein, tobe movement of less than one microliter of fluid. There is nothing inthe design of the nonpumping valve of FIG. 1 to limit nonpumping of thisvalue, except practicality. In theory the support rods could be made tobe exactly equal, so that there would be absolutely no change in thefree volume in chamber 12 when the closing means 13 is moved. Therewould still be some motion of fluid due to the motion of the closingmeans but this could be minimized by moving the closing means slowly. Inpractice, however, the support rods can only be made equal to withincertain tolerances. A volume change less than one microliter can beachieved. A smaller change could be achieved with greater difficultiesand higher cost if desired, but within the requirements of the samplingsystem it was not deemed necessary.

Once the problem introduced by a valve which inadvertently pumps fluidhas been realized, and a nonpumping valve designed, then a valve whichwill purposely pump a certain desired amount of fluid can be designed.Such a valve is shown in FIG. 2. The valve in FIG. 2 is almost identicalto that in FIG. 1 in that it contains a cylindrical valve chamber 28 ina valve body 29, and a closing means supported on two support rods 31and 32. Support rod 31 extends through the body of the valve 29 andthrough end plug 33 to the exterior of the velve, and support means 32extends through end plug 34 to the exterior of the valve. The valvechamber 28 has an opening 35 in one end of the chamber, and this openingexpands into a channel 36 which is connected through a second channel 37to one of the flattened sides of the valve body. In this case there isonly one channel 37 leading to one of the flattened surfaces. In otherdesigns, as will be discussed below, there can be two such channels. Theend of channel 37 adjacent to the flattened surface is again expanded tohouse a gasket which will allow sealing either to a pump or to a similarchannel, such as channel 22, in the nonpumping valve of FIG. 1. Thevalve chamber 28 also contains an opening 38 in its side which isconnected to the outside of the valve by a channel, not shown, in muchthe same way as that shown in FIG. 1B for the nonpumping valve. Also thevalve can be spring loaded with a spring 39 to be normally opened, asshown, or normally closed.

The main difference between this valve and the nonpumping valve is inthe relative size of the support rods. Support rod 31 has a largerdiameter than support rod 32, which means that as the closing means 38is moved to close the valve, the free volume in the valve chamber 28will be increased because the volume of support rod 32 which moves intothe valve chamber is less than the volume of support rod 31 which movesout of the valve chamber. By controlling the relative diameters of thesupport rods the desired change in the free volume in the valve chambercan be achieved. In the valve shown in FIG. 2 the increase in freevolume occurs when the valve is closed. This increase in free volumecauses suction in the opening 38 which draws a volume of fluid from theopening, and the channel which connects it to the outside of the valve,into the valve chamber. This aspiration can effectively remove anyexcess fluid that remains on the exterior lip of the intake-outputopening, or on the lip of a probe connected to the opening.

Optionally, the pumping valve could have been designed to pump oraspirate when the closing means was moved to open the valve. A valvedesigned to operate in this manner is shown in FIG. 3. This valve issimilar to the valve in FIG. 2 except that the position of the supportrods has been reversed. The support rod 40 with the smaller diameterextends through the opening 41 in the valve body 42, and passes throughthe valve body and through end plug 43 to the exterior of the valve. Thesupport rod 44, with the larger diameter, passes directly through endplug 45 to the exterior of the valve. Again, the opening 41 is expandedinto a channel 46 which is connected to one of the flat sides of thevalve by another channel 47. There is also an opening 48 in the side ofthe valve chamber 49. In this case, when the closing means 50 is movedto open the valve, the free volume in the valve cylinder is increasedcausing suction at opening 48. A spring 51 is included so that the valvecan be spring loaded in the closed position, as shown, or in the openposition.

The body of the pumping valve, such as the one shown in FIG. 3, and thebody of the nonpumping valve shown in FIG. 1 differ in another respect.The pumping valve has only one channel 47 leading from the expandedopening M. in the valve chamber. This means that in normal operationfluid enters the valve through opening 48 and passes through the valvechamber 49 and channels 46 and 47. When the closing means 50 closes thevalve, all motion of fluid through the valve ceases. The nonpumpingvalve of FIG. 1, however, has two channels leading from the expandedopening 19 so that there is a channel formed by channels 22, 20, and 21which passes directly through the body of the valve. This means thateven when the valve is closed there can be a flow of fluid through thebody of the valve. When the valve is opened a second stream of fluid isallowed to merge with the first stream of fluid, through opening 23. Asdesigned, then, the nonpumping valve can be used as an internal segmentof a transfer line, while the pumping valve must be used as the endsegment of a transfer line. This doesnt mean that the valves have to bedesigned this way. In practice it is often advantageous to construct thevalve cylinders of both the pumping and the nonpumping valves so thatthey are identical. In this case, the valve body 42 of the pumping valveshown in FIG. 3 would have two channels leading from the expendedopening 41, instead of just one. In normal operation one of these wouldbe blocked with an end plate of some sort, but at least the valve bodieswould be interchangeable. In many instances the blocked passage formedby the extra channel would be disadvantageous because of the difficultyof flushing and because of the ensuing contamination that would result.In practice it is also possible to design the nonpumping valve with justone channel rather than two. These considerations are controlled by theuse to which the valves will be put. One such use will be describedbelow.

Both the valves discussed above are to be constructed from suitablematerial, employing considerations known to those skilled in the art.While the design of the two valves discussed above is similar, this isdone merely for convenience. In these embodiments the valves are small,efficient, simple to construct and simple to clean. In addition, theyare of a design which makes them readily susceptible to nesting, eitherwith valves of a similar design or with the pump discussed below. Whennested with a pump the valves form a fluid handling and sampling system,in which similarly designed valves are convenient; but this does notmean that radically different designs employing the same principalscannot be used.

FIG. 4 illustrates one embodiment of a pump which can be used in aprecision fluid handling and sampling system. In this instance itconsists of a cylinder 59, a piston 60 and a means 61 of driving thatpiston. The pump cylinder 59 can be made to nest with the intake valve(or the intake-output valve if no intake valve is included) by havingthe channel 62, leading to the pump chamber 63, mate with one of thechannels in the intake valve such as channel 46 in FIG. 3. At the rearof the cylinder is a packing gland 73 to seal the piston rod. In oneembodiment, the end of the pump cylinder forming the forward wall of thepump chamber 63 is rounded so that no liquid will be trapped in thesquare corners inherent in a flat front wall. In another, the forwardwall is conically shaped for the same purpose. The piston 60 consists ofa deformable cap 64, a forward end plug 65, a hollow shaft 66, a rearend plug 67 and a screw shaft 68 running through the rear end plug 67,concentrically through hollow shaft 66, and into the deformable cap 64.The purpose of such a construction is to allow the shape of thedeformable cap to be changed by external means the screw 68 to conformto the forward and side walls of the pump chamber. The deformable cap64, made from any suitable deformable material, e.g., Teflon, can beshaped like a mushroom with its stem protruding through the forward plug65 into the hollow shaft 66. When the screw 68 is turned the stem of thedeformable cap 64 is drawn further into the hollow shaft 66 and the hoodof the mushroom is forced into contact with the forward plug 65. Thispressure changes the shape of the deformable cap, and forces the sidesof the deformable cap into contact with the walls of the cylinder 59.This is advantageous, since with repeated use the cap will wear to thepoint where it no longer fits snugly within the cylinder. When thishappens, leakage occurs which can cause errors limiting the precision ofthe instrument. In this embodiment, such constant wear can becompensated for, externally, by deforming the deformable cap to thepoint where it once again fits snugly with the walls of the cylinder.The fact that this can be done externally eliminates costly and timeconsuming dismantling of the device. The fact that the cap is made froma deformable material has a second advantage in that when the piston isbrought into contact with the rounded forward wall it is desirable thatthat portion of the cap furthest from the outlet channel makes contactwith the forward wall first. Then, as the piston is further drivenforward the cap deforms slightly until it mates fully with the forwardwall. In this way, fluid left at the bottom of the forward wall will beforced up into the channel, completely emptying the pump chamber 63.

The means 61 used to drive the piston can beany suitable means. Many areknown to those skilled in the art. In this embodiment, the hollowsupport rod 66 is linked to a ball screw by a pair of ball nuts. Theball nuts are threaded onto the ball screw, back to back, and areadjusted to take up all lost motion between the ball nuts and the ballscrew. The ball screw is driven through a set of pulleys and a timingbelt from a stepping motor. One step of the motor moves the piston adistance equivalent to a 20 microliter volume, such that the error inthis step is less than 0.5 microliter.

Since the system described above can be used to perform precise analytictests, it is important that it be kept clean at all times. When the pumpdraws in fluid, the cylinder walls are exposed to that fluid. When thefluid is discharged, a molecular film of fluid remains on the walls evenwhen the tightest fitting piston is used. This film would contaminatethe next, fluid taken into the pump, beyond the 0.02 percent to 0.03percent required in some tests. To overcome this, the pump must bedesigned to cleanse itself. The portion of the cylinder in front of thepiston can be cleansed by drawing a cleansing fluid through channel 62,in a manner which will be described below. Some method, however, must beprovided for cleansing the portion of the cylinder behind the piston.This can be done by providing an inlet port 69 to allow a cleansingliquid to pass through the hollow shaft 66 and through outlet 70 intothe area 71 behind the piston. Movement of the piston forward willautomatically draw the cleansing fluid through inlet port 69 into thearea 71, and movement of the piston backwards will force the cleansingfluid out through outlet port 72. At both inlet port 69 and outlet port72, suitable one way valves must be provided. Since the requirements ona valve used for this purpose are not stringent, any suitable valveknown to one skilled in the art will suffice. Optionally both inlet andoutlet ports could be in the valve cylinder.

FIG. is a schematic diagram of the elements described above as they canbe combined to form a fluid handling and sampling system. This systemcan be part of a fully automatic analytic instrument such as the onedescribed in US. Pat. application Ser. No. 753,197 wherein theoperational steps of the sampling system are programmed by somesequencing circuit which in itself operates in response to a codedinput, or it can be a simple manually operated system. The operationwould be much the same. For purposes of convenience, it will be assumedthat the sampling system comprises: a single intake-output valve 73; anintake valve 77 connected to a source of cleansing fluid; an intakevalve 78 connected to a source of buffer solution; and a pump. Thesystem can best be described in operation. Initially the intake-outputvalve 73 is opened and both intake valves 77 and 78 are closed. Theoperation begins with the closing of intake-output valve 73 and theopening of intake valve 78. By suction, provided by the pump 75, thebuffer solution is drawn from its source 79 into the intake valve 78through intake orifice 80, and into the pump chamber 81. In an operationwhere precise amounts of fluid are to be transferred from the source toa reaction chamber of some sort, it is usually necessary to keep thetransfer system free from gas bubbles so that the pummp will deliver anaccurate amount of fluid. In such a system a de-bubbler 82 can beprovided for this purpose; but this is optional. The design of thede-bubbler is standard and known to those skilled in the art.

In this embodiment the capacity of the sampling system is 5 milliliters.At this point the pump draws in l milliliter of buffer solution. Intakevalve 78 closes, intake-output valve 73 opens, and the pump dischargesthe buffer solution into a drain through sample probe 74. This is thebuffer flush. Intake-output valve 78 opens again, and pump 75 draws in avolume of buffer solution equal to 5 milliliters, less the volume of thesample fluid which will be required. In this embodiment the sample sizeusually can be varied from 20 to 500 microliters, in increments of 20microliters. Intake valve 78 closes, intake-output valve 73 opens, thesample transfer probe 74 moves from the drain and dips into the sample.It is important to note that, upon opening, intake-output valve 73 hasaspirated any excess fluid remaining on the lip of the transfer probe 74into the transfer probe, so that no fluid remains on the lip of thetransfer probe to contaminate or dilute the sample. The pump then drawsin the required sample volume to make up the total 5 milliliter volume.The sample probe then moves from the sample container to a position overthe receptacle which is to receive the sample and buffer fluids. Thesystem can be adapted to deliver this mixture in any way desired. Onepossibility is to inject the mixture into the analytic pack described inUS. Pat. No. 3,476,515. If this is the case, the transfer probe 74 canbe a hypodermic needle so that it can be inserted through the rubber damwhich forms the seal on the analytic pack. However, the application ofthis system is not intended to be limited to use with such an analyticpack. This system can be used to transfer fluid from a container, to anylocation, by any means desired by and known to those skilled in the art.

In the operation described above, the sample and buffer solution areusually discharged into the receptacle in two steps. This facilitatesthe use of a separation column in the receptacle; if such a column isdesired. In this embodiment most of the buffer solution is contained inthe pump 81. The sample is generally separate from the buffer solution,and of a volume small enough to be contained within the transfer probeand the associated transfer lines leading up to the pump chamber. Ineffect, this means that there is no mixing of the sample fluid and thebufier solution within the sampling system, even though the two fluidsare in contact with one another. Upon discharge, which is caused byreversing the action of the pump 75, the sample fluid is dischargedfirst, followed by the buffer solution. This means that, if a separationcolumn is used, the sample fluid will be washed through the separationcolumn by the buffer solution in a manner consistent with goodlaboratory practice.

The sample probe 74 is then positioned over the drain. Intake-outputvalve 73 closes, intake valve 77 opens and 1 milliliter of a washingfluid, which can be water, any solvent, or any fluid which will producethe desired flushing effect, is drawn from its source 83, optionallythrough a de-bubbler 84, through the intake orifice 85 in intake valve77 and into the pump chamber 81. Intake valve 77 closes, intake-outputvalve 73 opens, and the pump discharges the flushing fluid into thedrain. This is the water flush, which can be repeated as many times asdesired. At the end of the water flush the fluid handling system iscleaned and ready for intake of the buffer solution for the nextoperation. Actually, when only one buffer is being used, it is notnecessary to use a water flush step. The use of a water flush becomesnecessary when a number of buffer solutions are used. The water flush isincluded in this simple single buffer situation merely to illustrate theoperation of the system.

The pump shown in FIG. 5 is a piston pump such as that described in FIG.4. This is a convenient pumping system for the application describedabove, but it is not the only pumping system which can be used. Asdescribed above, the pump shown in FIG. 5 can be constructed so that itcan automatically cleanse the portions of the pump behind the piston 86.This is done by drawing some cleansing fluid into port 87 as the volumeof the pump chamber 81 is decreased, and forcing this cleansing fluidout through port 88 as the volume of the mixing chamber is increased.This double cleansing decreases contamination and insures the desiredprecision.

We claim:

1. A method of transferring a portion of the sample liquid contained ina source of sample liquid to a receptacle using a sampling systemcomprising a probe, a pump, an intake-output valve designed so that anincrease in the volume of liquid contained in said intakeoutput valveoccurs when said valve is opened, said in take-output valve beingconnected to said probe, and at least one intake valve connected betweensaid pump and said intake-output valve, said method comprising the stepsof a. aspirating any liquid present on the lip of said probe by virtueof previous operations of the sampling system by opening saidintake-output valve;

b. drawing a predetermined amount of said sample liquid into saidsampling system by positioning said probe over said source of sampleliquid, inserting said probe into said sample liquid and activating saidpump to provide suction;

c. discharging the sample liquid contained in said sampling system intosaid receptacle by positioning said probe over said receptacle andreversing the action of said pump; and

d. cleansing said pump, said intake valve, said intakeoutput valve, saidprobe and all connecting lines by drawing a cleansing liquid from itssource through said intake valve and into said pump by the suctionprovided by said pump, positioning said probe over a disposal zone, anddischarging said cleansing liquid through said probe into said disposalzone by reversing the action of said pump.

2. A method of transferring a portion of the sample liquid contained ina source of sample liquid along with at least one secondary liquid to areceptacle using a sampling system comprising a probe, a pump anintakeoutput valve designed so that an increase in the volume of liquidcontained in said intake-output valve occurs when said valve is opened,said intake-output valve being connected to said probe, and at least twointake valves connected between said pump and said intakeoutput valve,said method comprising the steps of a. drawing a predetermined amount ofsaid secondary liquid from its source into said pump by closing saidintake-output valve and activating said pump to provide suction;

b. aspirating any secondary liquid present on the lip of said probe byopening said intake-output valve;

c. drawing a predetermined amount of said sample liquid into saidsampling system by positioning said probe over said source of sampleliquid, inserting said probe into said sample liquid and activating saidpump to provide suction;

d. discharging the sample liquid and said secondary liquid contained insaid sampling system into said receptacle by positioning said probe oversaid receptacle and reversing the action of said pump; and

. cleansing said pump, said intake valve, said intake- 3. The method ofclaim 2 wherein, after the step of drawing a predetermined amount ofsaid sampling liquid from its source into said pump, the method furthercomprises the steps of a. discharging said secondary liquid through saidprobe into a disposal zone by positioning said probe over said disposalzone and reversing the action of said pump; and

a". drawing a second predetermined amount of said secondary liquid intosaid pump by closing said intake-output valve and activating said pumpto provide suction.

1. A method of transferring a portion of the sample liquid contained ina source of sample liquid to a receptacle using a sampling systemcomprising a probe, a pump, an intake-output valve designed so that anincrease in the volume of liquid contained in said intake-output valveoccurs when said valve is opened, said intake-output valve beingconnected to said probe, and at least one intake valve connected betweensaid pump and said intake-output valve, said method comprising the stepsof a. aspirating any liquid present on the lip of said probe by virtueof previous operations of the sampling system by opening saidintake-output valve; b. drawing a predetermined amount of said sampleliquid into said sampling system by positioning said probe over saidsource of sample liquid, inserting said probe into said sample liquidand activating said pump to provide suction; c. discharging the sampleliquid contained in said sampling system into said receptacle bypositioning said probe over said receptacle and reversing the action ofsaid pump; and d. cleansing said pump, said intake valve, saidintake-output valve, said probe and all connecting lines by drawing acleansing liquid from its source through said intake valve and into saidpump by the suction provided by said pump, positioning said probe over adisposal zone, and discharging said cleansing liquid through said probeinto said disposal zone by reversing the action of said pump.
 2. Amethod of transferring a portion of the sample liquid contained in asource of sample liquid along with at least one secondary liquid to areceptacle using a sampling system comprising a probe, a pump anintake-output valve designed so that an increase in the volume of liquidcontained in said intake-output valve occurs when said valve is opened,said intake-output valve being connected to said probe, and at least twointake valves connected between said pump and said intake-output valve,said method comprising the steps of a. drawing a predetermined amount ofsaid secondary liquid from its source into said pump by closing saidintake-output valve and activating said pump to provide suction; b.aspirating any secondary liquid present on the lip of said probe byopening said intake-output valve; c. drawing a predetermined amount ofsaid sample liquid into said sampling system by positioning said probeover said source of sample liquid, inserting said probe into said sampleliquid and activating said pump to provide suction; d. discharging thesample liquid and said secondary liquid contained in said samplingsystem into said receptacle by positioning said probe over saidreceptacle and reversing the action of said pump; and e. cleansing saidpump, said intake valve, said intake-output valve, said probe and allconnecting lines by drawing a cleansing liquid from its source throughsaid intake valve and into said pump by the suction provided by saidpump, positioning said probe over a disposal zone, and discharging saidcleansing liquid through said probe into said disposal zone by reversingthe action of said pump.
 3. The method of claim 2 wherein, after thestep of drawing a predetermined amount of said sampling liquid from itssource into said pump, the method further comprises the steps of a''.discharging said secondary liquid through said probe into a disposalzone by positioning said probe over said disposal zone and reversing theaction of said pump; and a'''' . drawing a second predetermined amountof said secondary liquid into said pump by closing said intake-outputvalve and activating said pump to provide suction.